Evening star. [volume] (Washington, D.C.) 1854-1972, 1887-07-09
WATERS OF STONE.
How the Biologist Studies Moumtaims
With the MICROSCOPE.
THE BEAUTIFUL APPEARANCE OF SECTION OF GRAN
TIE UNDER THE PETRoGRAPHER's GLAss-A COM
PARATIvELY NEW scrENcE-sLABs OF STONE ONE
FIvE-HUNpREpTH OF AN inch THICK

center what one might take at the first glance to
be soiled or gritty spot. "Look" he said, 70 THE
STAR reporter, and the reportorial eye was applied
to the glass 1t beheld brilliant sight, like that
seen in Kaleidoscope. The circular patch
focused by the object glass was filled with a sort
OF crazy quilt pattern. There was every variety OF
shape and color. The hues were OF most brilliant
description. The gritty-looking spot was section
OF Richmond granite, such as the new State
Department building is constructed OLA slab OF
stone so thin that five hundred OF them placed
| one upon another would not make an inch In
thickness, so thin as to be translucent. The
modern geologtst no longer confines himself to
tracing out terraces or paths OF glaciers or TO the
blow pipe or chemical analyses He takes the
mountains with him into his laboratory and there
studies them with microscope. The application
or the microscope TO the solution OF geological
problems Is comparatively new thing, and has
petrography.
SOLVING GEOLOGICAL PROBLEMS.
Many questions that vexed biologists for years
have been answered by the microscope. But many
| new problems have arisen out OF the discoveries
made by the use OF this instrument; so that the
geoog1St, instead OF finding himself In possession
OF key by which ali the wonderful story OF the
rocks can be read, has learned only that there are
deep and wonderful mysteries beyond his ken.
But the microscope has rendered great service TO
the geoogist In aiding not only In the solution OF
questions OF purely scientific character, but in de-
termfnfng the character OF building stones and
contributing in other ways to the economic branch
OF the science.
THE USE OF PoLARIzEp LIGHT.
ANY one with an eye to color looking through
the photographers microscope would conclude
too, that science had an aesthetic side. so The
STAR reporter thought his eye fingered over the
beautiful object disclosed by the glass that had
Deen arranged for him by Mr.. Geo. p. Merrill, of
the National Museum. MI. Merrill quickly dis
abused the reporters idea that any slab OF stone
placed under any microscope would reveal 10 the
eye crazy-qult patterns OF the richest colors. In
TACT the appearance OF the stone under the micro
scope would be changed very little from the ordl-
nary appearance. The bright colors are produced
py the use OF polariZed light. The microscope used
by the Photographer is manufactured especially
for him, and contains two Nicol prisms. A slab
or rock-sectiOn examined through the microscope
Without the prisms, may appear as one field OF
marking whatever. When the prisms are inserted
this cOlorless field becomes marked all over with
Irregular but sharply-defined marks each little
square, or diamond, or rhomboid, having its own
bright color. thirty years or more ago in England
rock sections were examined In transmitted light,
regarded as an amusing toy. The main effort was
TO discover something novel or beautiful The
posslbitieso OF microseopical photography were not
France, and now in this country, the value OF the
discovery thus stumbled upon has been realized.
the variety OF color and the grouping Of crystals
scientist a new chapter In the great book he
has to study: He applied himself at once to
these microscopic tablets. As he by years of
patient labor and wide Induction slowly determined
the meaning OF each color and form he was enabled
OF the earth.
STUDYING ROCK CRYSTALS.
The mineral constituents OF rocks examined in
transmitted light under the microscope exhibited
an altogether different character from that ordi-
narily presented when microscopically examined,
and the task OF gradually fixing their identity in
their new gu1Se was slow and tedious.
Through the agency OF micrOScODfcal METRO
graphy much has been added to our knowledge OF
the formation OF crystals. Mr.. Geo. Huntington
Williams, OF Johns Hopkins University, says that
the microscope now appears to afford almost the
only hopeful means OF dealing with the records OF
me staine strata OF the earth, which undoubt-
eddy contain the longest, as they do by far the
darkest, chapter OF its history. Much has already
been accomplished in this direction. The micro
scope has revealed differences in molecular struc>
ture of rocks that appeared identical when sub
1ected to chemical tests. Rocks supposed to have
been eruptive have been shown to be sedimentary,
the difference In character from other Sedimentary
rocks having been produced by great pressure or
other conditions affecting their molecular struc-
ture.
MAKING THE ROCK SECTIONS
An interesting part OF the work OF the petrogra-
pher is the preparation OF the rock sections or
thin slabs intended for micrOScOpical inspection.
At the National Museum, under the charge OF MI.
Merrill is small laboratory where these sections
are made. From q rock to be thus examined a
is ground nat and smooth on the nat side of q
large iron wheel covered with emery or corundum
Then the piece OF rock Is fastened upon a glass
slide, the smooth or ground surface being applied
to the glass and glued to 1t with Canadian balsam,
which is transparent and cOlorleSS. The other
side OF the stone is then ground down until the
section is translucent and thin enough to suit the
purpose OF the geOlOgtsr. A section is ground
down to thickness, or rather JhtnneSS OF one
flve-hundredth or one-Six-hundredthO OF an inch 1t
Is then removed from the piece of glass which it
is ground to glass slide and secured upon 1t by a
little square bit OF glass, itself marvel OF thin
ness that Is glued over the rock section with Cam
ad1an balSam. Thin as the rock section is Ii is q
solid mass, and not what it appears to the naked
eye, a mere gritty spot. Where the eye dlstln-
cuisines no form or color the microscope reveals
outlines and shades OF color.
BUBBLES OF LIQUID IN QUARTZ
In section OF granite sliced to the thinness of
beaten gold leaf can be detected between the sur
face little glObular cells. Here and there in the
quartz crystals are little cells filled with clear.
transparent liquid and trembling and dancing In
this liquid in each cell one can make out little
bubble OF air, Like the bubble In spirit-evel--air
that has been imprisoned since The time that
chaos reigned. These little cells with their spark
ling bubbles, are SO small that even under a
microscope OF high power they appear hardly as
large as pin head. This liquid Is said to be con-
densed carbontc acid gas or liquid carbon-dioxtde
''When you put a piece OF granite On stove or
upon some heated surface" said Mr.. Merrill, 'you
can hear little swapping reports. These are sue
cession OF little explosions caused by the expansion
OF the gas"